Design of an Intensified Reactor for the Synthetic Natural Gas Production through Methanation in the Carbon Capture and Utilization Context

112 páginasThe idea of a sustainable future has led to the exclusion of fossil fuels from development policies and the inclusion of low-carbon alternatives instead. The strategy must be holistic, as proposed by the carbon capture and utilization technologies alongside renewable energies. An example is converting CO2 into value-added products, such as CH4 or Synthetic Natural Gas (SNG), using surplus power of renewable alternatives, in a low-carbon footprint process. The chemical route for the synthesis of SNG from CO2 and H2 is a catalytic reaction known as CO2 methanation or Sabatier reaction. The methanation is an example of CO2 capture and utilization technologies' industrial application within the so-called Power-to-Methane (PtM) context. In this scenario, fixed bed reactors have been the reaction technology employed by default. However, their deficiency in handling the heat released from the highly exothermic Sabatier reaction or responding to the process' intermittency appropriately has been demonstrated. These drawbacks have aroused scientific interest in developing reactors better adapted to the PtM context demands. One approach is by intensifying the methanation process to increase the mass- and energy-transfer and improve its transient response. In this project, the phenomenological hot spots formation in fixed bed reactors used for the methanation industrial process was investigated through a parametric sensitivity analysis, simulating the reactor start-up. On the other hand, it was proposed a CFD simulation-aided conceptual design of a wall-coated reactor for the SNG production using an intensification strategy. The design was based on a reactor formed by single-pass and heat-exchanger stacked-plates. The reacting channel dimensions were defined, including the catalytic layer thickness, fulfilling a minimum quality threshold given by the CO2 conversion (≥ 95%). The proposed design was also intended to maximize the volume of processed gas while meeting the quality requirement, resulting in a throughput per reaction channel of ~12 ml/min. Likewise, the plates manifold geometry and dimensions that best promoted a flow rate uniform distribution were established as a function of the number of reacting channels. Finally, a preliminary dynamic analysis of the operation start-up and shutdown was performed, establishing that the designed reactor does not present a hysteresis behaviour, an ideal condition for intermittent environments.La idea de un futuro sostenible ha conllevado a suprimir el uso de combustibles de origen fósil de los planes de desarrollo y por el contrario incluir alternativas con baja huella de carbono. La estrategia debe ser holística, como lo proponen las tecnologías de captura y utilización de CO2 junto con las energías renovables. Un ejemplo es la conversión del CO2 en productos con valor agregado, como el CH4 o Gas Natural Sintético (GNS), utilizando la energía sobrante de las alternativas renovables, en un proceso con baja huella de carbono. La ruta química para síntesis de GNS a partir de CO2 e H2 es una reacción catalítica que se conoce como metanación de CO2 o reacción de Sabatier. La metanación es un ejemplo de aplicación industrial de las tecnologías de captura y utilización de CO2 en lo que también se conoce como el contexto Power-to-Methane (PtM). En ese ámbito, los reactores de lecho fijo han sido la tecnología de reacción utilizada por defecto. Sin embargo, se ha demostrado su incapacidad para manejar el calor liberado producto de la reacción de Sabatier (altamente exotérmica), o de responder apropiadamente a la intermitencia del proceso. Estas dificultades han despertado el interés científico por desarrollar reactores que se adapten mejor a las exigencias del contexto PtM. Una propuesta yace en intensificar el proceso de metanación, incrementando la transferencia de masa y energía además de mejorar su respuesta transitoria. En este proyecto se estudió, por un lado, la formación fenomenológica de puntos calientes en reactores de lecho fijo utilizados industrialmente para el proceso de metanación a través de un análisis de sensibilidad paramétrico, simulando el arranque del reactor. Por el otro lado, se propuso un diseño conceptual asistido por simulación CFD de un reactor de pared recubierta para la producción de GNS a través de una estrategia de intensificación. El diseño partió de un reactor formado por platos apilados de intercambio de calor de un solo paso. Se definieron las dimensiones del canal de reacción, incluyendo el grosor de la capa catalítica, que cumplían con el umbral mínimo de calidad dado por la conversión de CO2 (≥ 95%). El diseño propuesto también tuvo por objeto maximizar el volumen de gas procesado, cumpliendo a la vez con el requisito de calidad, lo que resultó en un rendimiento por canal de reacción de ~12 ml/min. Así mismo se estableció la geometría y dimensiones del colector del plato que mejor favorecían una distribución uniforme de la velocidad del flujo en función del número de canales de reacción. Por último, se realizó un análisis dinámico preliminar del arranque y apagado de la operación, estableciendo que el reactor diseñado no presenta un comportamiento de histéresis, ideal para un entorno con alta intermitencia.Maestría en Diseño y Gestión de ProcesosMagíster en Diseño y Gestión de Proceso

Modelagem matemática e simulação numérica de reatores de leito fluidizado borbulhante e incorporação em simulador de processos comercial

Orientador: Maria Teresa Moreira RodriguesTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Reatores de leito fluidizado são muito importantes na indústria química, devido sua capacidade de gerenciamento de calor e outros aspectos. Porém, apesar da modelagem matemática e simulação numérica desses reatores terem sido feitos com relativo sucesso ao longo dos últimos cinquenta anos, há uma falta de bons modelos que permitam que sejam simulados em simuladores de processo. O objetivo desse trabalho é desenvolver um modelo matemático baseado na fluidização borbulhante, considerando escoamento não-ideal, transferência de calor e massa entre gás e partículas. O modelo também aborda reações químicas múltiplas e utiliza estratégia sequencial-modular para prover bons resultados e permitir que seja simulador de dentro de simuladores de processo comerciais. Primeiro, o comportamento fluidodinâmico da fluidização borbulhante foi analisado e o conjunto bolha-nuvem-emulsão foi tratado como um sistema em modo transiente, enquanto que a emulsão foi tratada como um escoamento de gás em estado estacionário. Em seguida, outras regiões dentro do reator também foram consideradas, como distribuidor, superfície livre e ciclones. Uma vez que o padrão de escoamento foi determinado, o sistema bolha-nuvem-emulsão é modelado como um modelo de compartimentos, no qual o gás em circulação fechada escoa entre tanques agitados catalíticos e leito fixo até o tempo de residência ser atingido. O modelo foi aplicado em um reator de leito fluidizado borbulhante industrial real como estudo de caso, um reator para síntese de anidrido ftálico via oxidação de naftaleno. Esse sistema tem modelos cinéticos desenvolvidos desde os anos 60 e baseados em hipóteses simplificadoras que não condizem com a realidade, então um modelo cinético de pseudo-primeira ordem foi ajustado à composição experimental da saída do reator com o propósito de obter um modelo cinético válido para as simulações realizadas posteriormente, e esse procedimento foi chamado de calibração do modelo. Resultados das simulações e suas análises permitiram concluir que o modelo proposto é fisicamente consistente e tem potencial de ser utilizado para outros processos químicos que utilizam reatores semelhantesAbstract: Fluidized Bed Reactors are very important in the chemical industry due to their capability of heat management and other features. However, although mathematical modeling and numerical simulation of such reactors have been done with relative success over the last fifty years, there is an absence of a good model to allow them to be accurately simulated into process flowsheets. The objective of this work is the development of a mathematical model based on bubbling fluidization, accounting for non-ideal flow, heat and mass transfer between gas and particles. The model also deals with multiple reactions and uses sequential modular strategy to provide good results and allow it to be simulated from within commercial process simulators. First, the fluid dynamic behavior of the bubbling fluidization was analyzed and the set bubble-cloud-wake was treated as a system under transient mode, while the emulsion was treated as a steady state flow of gas. Next, the other regions inside the reactor were also considered, such as distributor, freeboard and cyclones. Once the flow pattern was determined the system bubble-cloud-wake is modeled as a compartment model, as a closed loop gas flow between catalytic stirred tanks and packed bed until the residence time is achieved. The model was applied to a real industrial bubbling fluidized reactor as case study, a reactor for synthesis of phthalic anhydride via naphthalene oxidation. This system has kinetics models developed since the 1960¿s and based on simplifying hypothesis which do not match reality, so pseudo-first order kinetics model were fit to experimental exit reactor composition in order to obtain a kinetic model valuable for the simulations performed after, and this procedure was called model calibration. Results of simulations and its analysis allow the conclusion that the proposed model is physically consistent and has potential to be applied in other chemical processes which use similar reactorsDoutoradoEngenharia QuímicaDoutor em Engenharia Química140463/2015-1CNP

Application of Artificial Neural Networks to Chemical and Process Engineering

The accelerated use of Artificial Neural Networks (ANNs) in Chemical and Process Engineering has drawn the attention of scientific and industrial communities, mainly due to the Big Data boom related to the analysis and interpretation of large data volumes required by Industry 4.0. ANNs are well-known nonlinear regression algorithms in the Machine Learning field for classification and prediction and are based on the human brain behavior, which learns tasks from experience through interconnected neurons. This empirical method can widely replace traditional complex phenomenological models based on nonlinear conservation equations, leading to a smaller computational effort – a very peculiar feature for its use in process optimization and control. Thereby, this chapter aims to exhibit several ANN modeling applications to different Chemical and Process Engineering areas, such as thermodynamics, kinetics and catalysis, process analysis and optimization, process safety and control, among others. This review study shows the increasing use of ANNs in the area, helping to understand and to explore process data aspects for future research

Solid sponges as support for heterogeneous catalysts in gas-phase reactions

Solid sponges combine large specific surface areas and low pressure losses with excellent heat transport properties. Thus, they are promising catalyst supports for endo- and exothermic processes. Nevertheless, design tradeoffs regarding the porosity and window diameter of solid sponges with respect to high catalyst densities, low pressure losses, and high effective thermal conductivities remain unsolved. Therefore, a 2-d pseudo-homogeneous multi-scale reactor model for solid sponges is developed in this work. The model is validated against polytropic lab-scale experiments for the methanation of carbon dioxide in a fixed-bed reactor. In order to quantify and analyze the design tradeoffs, the model is used to solve the outlined multi-objective optimization problem. Moreover, tailored graded solid sponges with an optimal porosity distribution in the radial direction are introduced to successfully resolve the existing design tradeoffs

Application of method of lines in chemical engineering problems

In this work, two problems in chemical engineering are studied and solved. Estimation of an important parameter of dust explosions, the deflagration index kST , and a study of unsteady state with axial diffusion Plug Flow Reactors are presented. Both problems are approached by characterizing the physical phenomena involved with suitable transport equations. Such equations have been developed with the synergy of both consolidated theoretical models and ad hoc assumptions and semi-empiric approaches, according to the specific problem analyzed. The final equation systems result in a system of non-linear Partial Differential Equations. The numerical solution of such equations has been performed by implementing the Method of Lines, a numerical method based on the discretization of spatial derivative operators, transforming a system of PDEs into a system of ODEs or DAEs. The resulting ODEs/DAEs systems have been implemented and solved inside MAT LABTMenvironment. The Method of Lines is presented for uniform and non-uniform grids, generalized with the use of spatial derivatives discretization stencils of several orders of accuracy. For the estimation of kST , we validated the model with 8 organic dust: Aspirin, Cork, Corn starch, Niacin, Polyethylene, Polystyrene, Sugar and Wheat flour. Results showed an interesting match between experimental and simulated data: predictions for the deflagration index were good, while the evolution of process variables (such as the temperature of the gas phase), still leaves room for improvements. For the PFR study, we propose 1-D models, taking in account the reactor start-up, thermal and material axial diffusion, and the presence of a heating/cooling system. In order to judge the quality of the results, we took as case study a reaction well studied in the literature over the years: the oxidation of Naphthalene. We developed the so-called Runaway Boundaries for the reaction considered. Our results found good matches with the available literature data and analysis. We also noticed a shifting of the Runaway Boundaries when considering a more realistic heating/cooling system

Application of method of lines in chemical engineering problems

In this work, two problems in chemical engineering are studied and solved. Estimation of an important parameter of dust explosions, the deflagration index kST , and a study of unsteady state with axial diffusion Plug Flow Reactors are presented. Both problems are approached by characterizing the physical phenomena involved with suitable transport equations. Such equations have been developed with the synergy of both consolidated theoretical models and ad hoc assumptions and semi-empiric approaches, according to the specific problem analyzed. The final equation systems result in a system of non-linear Partial Differential Equations. The numerical solution of such equations has been performed by implementing the Method of Lines, a numerical method based on the discretization of spatial derivative operators, transforming a system of PDEs into a system of ODEs or DAEs. The resulting ODEs/DAEs systems have been implemented and solved inside MAT LABTMenvironment. The Method of Lines is presented for uniform and non-uniform grids, generalized with the use of spatial derivatives discretization stencils of several orders of accuracy. For the estimation of kST , we validated the model with 8 organic dust: Aspirin, Cork, Corn starch, Niacin, Polyethylene, Polystyrene, Sugar and Wheat flour. Results showed an interesting match between experimental and simulated data: predictions for the deflagration index were good, while the evolution of process variables (such as the temperature of the gas phase), still leaves room for improvements. For the PFR study, we propose 1-D models, taking in account the reactor start-up, thermal and material axial diffusion, and the presence of a heating/cooling system. In order to judge the quality of the results, we took as case study a reaction well studied in the literature over the years: the oxidation of Naphthalene. We developed the so-called Runaway Boundaries for the reaction considered. Our results found good matches with the available literature data and analysis. We also noticed a shifting of the Runaway Boundaries when considering a more realistic heating/cooling system

CFD simulation of transport and reaction in cylindrical catalyst particles

Multitubular packed bed reactors with low tube-to-particle diameter ratios (N) are especially selected for strongly endothermic reactions such as steam reforming and propane dehydrogenation. For low N tubes, the presence of the wall causes changes in bed structure, flow patterns, transport rates and the amount of catalyst per unit volume. In particular, the particles close to the wall will behave differently to those inside the bed. The problem is that, due to the simplifying assumptions, such as uniform catalyst pellet surroundings, that are usual for the current pseudo-continuum reactor models, the effects of catalyst pellet design changes in the near-wall environment are lost. The challenge is to develop a better understanding of the interactions between flow patterns, species pellet diffusion, and the changes in catalyst activity due to the temperature fields in the near wall region for the modeling and design of these systems. To contribute to this improved understanding, Computational Fluid Dynamics (CFD) was used to obtain detailed flow, temperature, and species fields for near-wall catalyst particles under steam reformer and propane dehydrogenation reactor inlet conditions. As a first step, a reduced size model was generated by only considering a 120 degree segment of an N = 4 tube, and validated with a larger size complete bed model. In terms of the flow and temperature contours and profiles, the complete tubes can be represented well by the reduced size models, especially focusing on the center particles positioned in the middle of the near wall region. The methane steam reforming heat effects were implemented by a user-defined code with the temperature-dependent sinks in the catalyst particles, near to the pellet surfaces for different activity levels. For the sinks terms, bulk phase species concentrations were used in the reaction rates, and with the reaction heat effects inclusion, significant pellet sensitivity was observed with different activity levels. Furthermore, non-symmetric temperature fields in and around the near wall particles were noticed as contrary to the conventional approach. In order to focus on the 3D intra-pellet distributions of temperature and species, diffusion and reaction were coupled to the external flow and temperature fields by user-defined code. Strong deviations from uniformity and symmetry on the temperature and species distributions existed as a result of the strong wall heat-flux into the particles Additionally, the pseudo-continuum type of packed bed model was created, which considers the simplified environment for the reacting particles. The results obtained by the diffusion reaction application in the 3D discrete packing model could not be re-produced by the conventional simplified pseudo-continuum approach, no matter which parameter values were chosen for the latter. The significance of these observations is that, under the conventional assumption of symmetric particle surroundings, the tube wall temperature and reaction rates for catalyst particles can be incorrectly evaluated and important design considerations may not be well predicted, thus, negative consequences on the plant safety and efficiency may be observed

Industrial Chemistry Reactions: Kinetics, Mass Transfer and Industrial Reactor Design

Nowadays, the impressive progress of commercially available computers allows us to solve complicated mathematical problems in many scientific and technical fields. This revolution has reinvigorated all aspects of chemical engineering science. More sophisticated approaches to catalysis, kinetics, reactor design, and simulation have been developed thanks to the powerful calculation methods that have recently become available. It is well known that many chemical reactions are of great interest for industrial processes and must be conducted on a large scale in order to obtain needed information in thermodynamics, kinetics, and transport phenomena related to mass, energy, and momentum. For a reliable industrial-scale reactor design, all of this information must be employed in appropriate equations and mathematical models that allow for accurate and reliable simulations for scaling up purposes. The aim of this proposed Special Issue was to collect worldwide contributions from experts in the field of industrial reactor design based on kinetic and mass transfer studies. The following areas/sections were covered by the call for original papers: Kinetic studies on complex reaction schemes (multiphase systems); Kinetics and mass transfer in multifunctional reactors; Reactions in mass transfer-dominated regimes (fluid–solid and intraparticle diffusive limitations); Kinetic and mass transfer modeling using alternative approaches (ex. stochastic modeling); Simulations in pilot plants and industrial-sized reactors and scale-up studies based on kinetic studies (lab-to-plant approach)

Effect of nutritional factors on the growth and production of biosurfactant by Pseudomonas aeruginosa strain 181

The growth and production of biosurfactant by P. seudomonas aeruginosa (181) was dependant on nutritional factors. Among the eleven carbon sources tested, glucose supported the maximum growth (0.25 g/L) with the highest biosurfactant yield and this was followed by glycerol. Glucose reduced the surface tension to 35.3 dyne/ cm and gave an E24 reading of 62.7%. Butanol gave the lowest growth and had no biosurfactant production. For the nitrogen sources tested, casamino acid supported a growth of 0.21 g/L which reduced the surface tension to 41.1 dyne/cm and gave an E24 reading of 56%. Soytone was assimilated similarly, with good growth and high biosurfactant production. Corn steep liquor gave the lowest growth and did not show any biosurfactant activity